This invention relates to an endoscope having a direction indication mechanism by which the actual direction of each portion of an image obtained by the endoscope can be confirmed.
Generally, an endoscope comprises a body, an insertion portion extending from the body, and a rigid tip member mounted on a distal end of the insertion portion. An inspection window is provided at a distal end face of the tip member. An image entering from the inspection window is observed from an ocular portion of the body through an image guide passing through the insertion portion.
When the insertion portion of the endoscope is inserted into a tube of a complicated shape so as to observe the inner surface of this tube, the actual direction of each portion of an image obtained or picked up by the endoscope is not confirmed, for example, because of a torsion of the insertion portion. Therefore, even if a defect can be found on the inner surface of the tube, the direction in which this defect exists (that is, whether the defect is in the right, the left, the upper or the lower direction) is not confirmed.
In order to overcome such a disadvantage, there have been proposed endoscopes, as disclosed in Japanese Laid-Open Patent Application Nos. 62-63910 and 2-68024, which incorporate a direction indication mechanism for confirming the actual direction of each portion of a picked-up image.
The direction indication mechanism of the former publication is provided within a tip member of the endoscope as shown in FIGS. 1 and 3 of this publication, and more specifically this mechanism is disposed between an inspection window and a distal end of an image guide, and has a ball 12 which is limited in axial movement by a pair of transparent plates 11 but is movable in circumferential and radial directions. Therefore, part of this ball can be observed as part of an image from an ocular portion provided on a body of the endoscope. The ball is always located at the lower side by gravity, and therefore the upper and lower directions with respect to the image can be confirmed by observing the ball. In embodiments shown in FIGS. 8 and 9 of this publication, there is used a transparent disk 15 rotatably supported by an annular bearing 14. The center of gravity of this disk 15 is eccentric from the axis of rotation thereof, and a direction indication mark 16 is provided on that portion of this disk always kept at the lower side. In the endoscope disclosed in this publication, however, since the direction indication mechanism is provided between the inspection window and the distal end of the image guide, this mechanism can not be detached. Therefore, even when the direction indication is not needed, the field of vision is narrowed by the ball 12 and the mark 16, so that the observation can not be carried out satisfactorily.
The direction indication mechanism disclosed in the latter publication includes a forwardly-extending wire 26 secured to a tip member of the endoscope, and a weight 28 secured to a distal end of this wire. The wire is elastically deformed by the weight. The direction of deformation of the wire is the direction of the gravity, and by observing this, the upper and lower directions with respect to the image can be confirmed. In the direction indication mechanism of this publication, there has been encountered a problem that since the wire hangs down across the field of vision, the image can not be observed satisfactorily. This publications show in FIGS. 1, 4, 6 and 9 embodiments in which the proximal portion of the wire is releaseably connected to the tip member.